Content distribution system

ABSTRACT

An object of the present disclosure is to distribute content with a high quality and low latency without being limited by a low-rate and unstable network and a low-capacity reception-side edge servers while maintaining sufficient traffic reduction effects. 
     A content distribution system according to the present disclosure converts part of communication for distribution into multicast communication. In the content distribution system, a transmission-side edge server (UC/MC) generates and transmits a plurality of multicast streams having different transfer rates for the same input content, and a reception-side edge server (MC/UC) selects and receives a multicast stream having a desired transfer rate among the plurality of transmitted multicast streams.

TECHNICAL FIELD

The present disclosure relates to a method for converting traffic of aplurality of unicast streams having the same content identifier fordifferent destinations from unicast into multicast, from multicast intomulticast, and from multicast into unicast.

BACKGROUND ART

HTTP streaming methods such as HLS (NPL 1) and MPEG-DASH (NPL 2) areknown for video distribution using HTTP. When the same content, such aslive content, is distributed simultaneously to a large number of usersin HTTP streaming, loads on the server and the network are easily likelyto increase because the content is communicated from the server toindividual clients in unicast. If overload on the server or networkcongestion occurs, Quality of Experience (QoE) in viewing deteriorates,causing low video quality, video stopping, and the like. In order toprevent deteriorating QoE, there is a technique of converting part ofcommunication for distribution into multicast communication (NPL 3 andNPL 4).

FIG. 1 illustrates an example of a technique of converting part of thecommunication for distribution into multicast communication. In thistechnique, an edge server (UC/MC) 91 and a plurality of edge servers(MC/UC) 92 are disposed between an origin server 93 and pieces of userequipment (UE) 94, and multicast communication is performed between theorigin server 93 and the pieces of UE 94. In this manner, the amount oftraffic resulting from transmission of the origin server and the edgeserver (UC/MC) can be reduced to about 1 per the number of pieces of UE,in comparison with unicast distribution, while keeping the past HTTPinterface for the interface between the origin server and the UE. As aresult, the load imposed on the origin server can be reduced and stableand high-quality live video distribution to the UE can be achieved whileusing video distribution servers and web-based players in the prior art.

Video distribution based on HTTP contains a function of preparing avideo having a plurality of image qualities and selecting an appropriateimage quality that is called Adaptive Bit Rate (ABR) according to theband of the network (NPL 1 and NPL 2). Thus, by transmitting a videowith a low image quality and a low transfer rate on the network with anarrower band, the receiver can play back the video with nointerruption.

CITATION LIST Non Patent Literature

-   NPL 1: RFC8216-   NPL 2: ISO/IEC23009-   NPL 3: Fujiwara et al., IEICE technical report, CQ2019-102, 2019-   NPL 4: Fujiwara et al., IEICE technical report, CQ2019-72, 2019

SUMMARY OF THE INVENTION Technical Problem

In the technique of converting part of the communication fordistribution into multicast communication, a limitation on performancecaused by the network or the edge server (MC/UC) occurs. Specifically,because it is necessary to match the transmission rate of multicastpackets to the network with the lowest rate or the reception capacity ofthe edge server (MC/US), the overall transmission latency increases dueto the network with the lowest rate or the edge server (MC/US) with thelowest reception capacity (FIG. 2 ).

In addition, in order to prevent the increase in the latency, ahigh-rate and QoS-manageable network needs to be used as a network formulticast transmission, and high-performance equipment with highreception capacity needs to be used as an edge server (MC/UC).

With respect to the ABR mentioned above, it is difficult to provide ahigh image quality video to a reception terminal connected to anarrow-band network because the image quality is switched to a low imagequality.

An object of the present disclosure is to provide high-quality andlow-latency content distribution to a high-rate and highly stablenetwork or a high-capacity reception-side edge server and provide stablecontent distribution to a low-rate and unstable network or alow-capacity reception-side edge server at the same time, without beingrestricted by the low-rate and unstable networks or the low-capacityreception-side edge servers, while maintaining sufficient trafficreduction effects brought about by multicast.

Means for Solving the Problem

To achieve the above object, according to the present disclosure, in acontent distribution system for converting part of communication fordistribution into multicast communication, a transmission-side edgeserver (UC/MC) generates and transmits a plurality of multicast streamshaving different transfer rates for the same input content, and areception-side edge server (MC/UC) selects and receives a multicaststream having a desired transfer rate among the plurality of transmittedmulticast streams.

A content distribution system according to the present disclosure is acontent distribution system for converting part of communication fordistribution into multicast communication. The content distributionsystem includes a transmission-side edge server that converts unicastcommunication into multicast communication and performs transmission toa multicast communication network, and a reception-side edge server thatconverts the multicast communication transmitted on the multicastcommunication network into unicast communication. The transmission-sideedge server generates and transmits a plurality of multicast streamshaving different transfer rates for the same input content, and thereception-side edge server selects and receives a multicast streamhaving a desired transfer rate among the plurality of transmittedmulticast streams.

A content distribution method according to the present disclosure is amethod performed by a content distribution system for converting part ofcommunication for distribution into multicast communication. The contentdistribution system includes a transmission-side edge server thatconverts unicast communication into multicast communication and performstransmission to a multicast communication network, and a reception-sideedge server that converts the multicast communication transmitted on themulticast communication network to unicast communication. Thetransmission-side edge server generates and transmits a plurality ofmulticast streams having different transfer rates for the same inputcontent, and the reception-side edge server selects and receives amulticast stream having a desired transfer rate among the plurality oftransmitted multicast streams.

An edge server apparatus according to the present disclosure is includedin a content distribution system for converting part of communicationfor distribution into multicast communication. The edge server apparatusis a transmission-side edge server that converts unicast communicationinto multicast communication and performs transmission to a multicastcommunication network, generates a plurality of multicast streams havingdifferent transfer rates for the same content received in the unicastcommunication, and transmits the plurality of generated multicaststreams to the multicast communication network.

An edge server apparatus according to the present disclosure is an edgeserver apparatus included in a content distribution system forconverting part of communication for distribution into multicastcommunication. The edge server apparatus is a reception-side edge serverthat converts the multicast communication transmitted on a multicastcommunication network into unicast communication, receives a pluralityof multicast streams having different transfer rates from the multicastcommunication network, and selects and receives a multicast streamhaving a desired transfer rate among the plurality of received multicaststreams.

A program according to the present disclosure is a program that causesthe computer to operate each function of the apparatus of the presentdisclosure, and a program that causes the computer to perform each stepof the method of the present disclosure.

Effects of the Invention

The present disclosure can provide high-quality and low-latency contentdistribution to a high-rate and highly stable network or a high-capacityreception-side edge server and provide stable content distribution to alow-rate and unstable network or a low-capacity reception-side edgeserver at the same time, without being restricted by the low-rate andunstable networks or low-capacity reception-side edge servers, whilemaintaining sufficient traffic reduction effects brought about bymulticast.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of a system configuration in which part ofthe communication for distribution is converted into multicastcommunication.

FIG. 2 is a diagram illustrating an issue of the technique of convertingpart of the communication for distribution into multicast communication.

FIG. 3 is an example of a system configuration illustrating an overviewof the present disclosure.

FIG. 4 illustrates a first example of a control sequence for a multicaststream.

FIG. 5 illustrates a second example of a control sequence for amulticast stream.

FIG. 6 is an example of a system configuration of a case of transmittinga multi-layer multicast stream.

FIG. 7 illustrates an example in which content (file/stream) has beendivided.

FIG. 8 is an example of a layer pattern in which the number of receivinggroups is two.

FIG. 9 is an example of a layer pattern in which the number of receivinggroups is three.

FIG. 10 is an example of a configuration of an edge server (UC/MC) andan edge server (MC/UC).

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the drawings. Further, the present disclosureis not limited to the embodiments described below. These examples of theembodiments are merely examples, and the present disclosure can beimplemented in forms in which various modifications and improvements areadded based on knowledge of those skilled in the art. Constituentelements with the same reference signs in the specification and thedrawings are assumed to be the same constituent elements.

For the same content before conversion, an edge server (US/MC) generatesand transmits multiple multicast streams with different transmissionrates, and another edge server (MC/UC) selectively receives receivablemulticast streams.

FIG. 3 illustrates an overview of the present disclosure. The edgeserver (UC/MC) 91 generates a stream 1 and a stream 2 for file 1. Thestream 1 is subject to high-rate packet transmission, and the stream 2is subject to low-rate packet transmission. An edge server (MC/UC) 92Ais a device for a high-rate or high-performance network for multicastreception and selectively receives the stream 1. Another edge server(MC/UC) 92B is a device for a low-rate or low-performance network formulticast reception and selectively receives the stream 2. Thus, contentcan be distributed with a low latency according to the receptioncapacities of the network or the edge servers (MC/UC) 92A, 92B, and 92C.

The multiple multicast streams, such as the stream 1 and stream 2, maybe selectively received and transferred via a device such as the edgeservers (MC/UC) 92 and a router 95 in the network when part of theheaders of the packets, other than data, such as source addresses, groupaddresses, ports, or priorities are different in the streams in additionto the transmission rates.

The selective multicast reception of streams with different sourceaddresses or group addresses can be controlled by the edge server(MC/UC) 92 using a dynamic multicast route control technique such as anInternet Group Management Protocol (IGMP) or Multicast ListenerDiscovery (MLD). Thus, only a stream selected by the edge server (MC/UC)92 is selectively transferred by network equipment, such as the router95, and thus a stream not selected by the edge server (MC/UC) 92 is notdistributed to the corresponding edge server (MC/UC) 92. Also forcontrol of a static multicast route, a pseudo-dynamic multicast routecan also perform control in conjunction with an operation system of thenetwork equipment. In a case of a static multicast route, a route forhigh-rate streams and a route for low-rate streams may be set inadvance. The number of streams may be three or more.

As a result, the amount of traffic resulting from transmission of theorigin server 93 and the edge server (UC/MC) 91 can be reduced to thenumber of multicast streams for the content for approximately the numberof pieces of UE, compared to unicast distribution. While the amount oftraffic increases to approximately a multiple of the number of multicaststreams of the content, compared to that in the multicast conversiontechniques of the related art (NPL 3 and NPL 4), a sufficient amount oftraffic with respect to the server and the network can sufficiently bereduced, considering the fact that the number of pieces of UE is verylarge.

When there is no UE 94 to connect, the edge server (MC/UC) 92C does notreceive stream distribution and thus has no streams to receive, but,when there is the UE 94 to connect, the edge server can receive anystream by performing similar processing to that of any of the edgeserver 92A or 92B. Further, the number of edge servers (MC/UC) 92 is notlimited to three, and may be plural. In the present disclosure, themultiple edge servers (MC/UC) 92A, 92B, and 92C will be denoted as anedge server (MC/UC) 92 if there is no need to distinguish them from eachother.

The router 95 that supports multicast is installed on the networkbetween the edge server (UC/MC) 91 and the edge server (MC/UC) 92, and amulticast stream to be distributed to an edge server (MC/UC) 92 may beselected by the router 95. In addition, the selection may also be madein response to a request of an edge server (MC/UC) 92.

Sequence

Sequence Pattern 1: Selection of Edge Server (MC/UC) 92

FIG. 4 illustrates an example of a control sequence for a multicaststream.

The edge server (MC/UC) 92 requests stream information such as thetransmission rate, the source (S) address, the group (G) address, theport, the priority, and the like of content from the edge server (UC/MC)91 in “(1) multicast stream information request”. Here, the requestdestination of “(1) multicast stream information request” may be adifferent apparatus from the edge server (UC/MC) 91 that manages themulticast stream information. Further, “(1) multicast stream informationrequest” may be made using a content request from the UE 94 connected tothe edge server (MC/UC) 91.

The edge server (UC/MC) 91 responds to the edge server (MC/UC) 92 for aplurality of pieces of stream information to be distributed with “(2)multicast stream information response”. Here, the response source of“(2) multicast stream information response” may be a different apparatusfrom the edge server (UC/MC) 91 that manages the multicast streaminformation. The edge server (MC/UC) 92 selects a receivable and optimalsingle stream from the plurality of received pieces of multicast streaminformation. For example, the edge server (MC/UC) 92 selects areceivable and optimal single stream based on information such as anetwork connection rate, whether the network connection is by wired orwireless communication, specifications and loads of computationresources such as the CPU and the memory, the past packet receptionsituations (such as whether an error has occurred), or an upper limitset from the outside or made in a manual manner, and the like.

The edge server (MC/UC) 92 requests distribution of the selectedmulticast stream as multicast Join from the router 95, or the likedisposed on the network that performs transfer in multicast using “(3)Join processing”. This allows distribution of the multicast streamselected from the router 95 or the like. For “(3) Join processing”, forexample, a protocol such as IGMP or MLD can be used.

The edge server (MC/UC) 92 requests distribution of the selectedmulticast stream from the edge server (UC/MC) 91 using “(4) multicaststream request”. Here, the request destination of “(4) multicast streamrequest” may be a different apparatus from the edge server (UC/MC) 91that manages the multicast stream information. In this case, theapparatus that manages multicast stream information can requestdistribution of the multicast stream requested from the edge server(MC/UC) 92 with respect to the edge server (UC/MC) 91 in continuation of“(4) multicast stream request”.

Here, the order of “(3) Join processing” and “(4) multicast streamrequest” may be reversed. In addition, “(3) Join processing” may beomitted in the case of a network on which a static multicast route hasbeen built. Furthermore, “(1) multicast stream information request” and“(2) multicast stream information response” can be omitted if themulticast stream information is known or predetermined.

In addition, “(2) multicast stream information response” may include thefact that distribution has been completed if the corresponding multicaststream has already been distributed due to a request from another edgeserver (MC/UC) 92. “(4) multicast stream request” may be omitted.

The edge server (UC/MC) 91 distributes the requested stream in “(5)multicast stream”, and the edge server (MC/UC) 92 receives the stream.When the corresponding multicast stream has already been distributed dueto a request from another edge server (MC/UC) 92, the new distributioncan be omitted.

The edge server (MC/UC) 92 can notify the edge server (UC/MC) 91 ofstopping or completion of the reception of the multicast stream using“(6) notification of stop/completion of reception of multicast stream”.Here, the notification destination of “(6) notification ofstop/completion of reception of multicast stream” may be a differentapparatus from the edge server (UC/MC) 91 that manages the multicaststream information. In this case, the apparatus that manages themulticast stream information can notify the edge server (UC/MC) 92 ofthe multicast stream information notified from the edge server (MC/UC)91 in continuation of “(6) notification of stop/completion of receptionof multicast stream”. Further, with respect to (6), in a case in which“(4) multicast stream request” times out, or a long time is taken for“(5) multicast stream”, continuation of viewing such as a keepalive maybe notified from the edge server (MC/UC) 92 in the middle of receiving“(5) multicast stream” and may be used as a substitute for the timeoutor in combination. Further, in a case in which distribution of the samemulticast stream to other edge servers (MC/UC) 92 continues, thedistribution is not stopped, and only in a case in which reception byall edge servers (MC/UC) 92 is stopped/finished, the distribution of themulticast can be stopped.

The edge server (MC/UC) 92 notifies the router 95 on the network thatperforms transfer in multicast of the fact that the reception of theselected multicast stream has finished in multicast Join, or the like,using “(7) Leave processing”. This allows the distribution of themulticast stream selected from the router 95 or the like to be stopped.For “(7) Leave processing”, for example, a protocol such as IGMP or MLDcan be used.

Here, the order of “(6) notification of stop/completion of reception ofmulticast stream” and “(7) Leave processing” may be reversed. Inaddition, “(7) Leave processing” may be omitted in the case of a networkon which a static multicast route has been built.

A single stream may be composed of multiple sub-streams. In a case ofaddresses, for example, a single combination (S1, G1) may be regarded asa single stream 1, and a combination of multiple addresses {(S1, G1),(S2, G2)} may be regarded as a single stream.

Multiple files may be processed as the same multicast stream. Forexample, there is a case in which one piece of content is stored asdivided multiple files in the origin. In this case, they can be regardedas the same multicast stream in terms of the common URL, or the like.

Sequence Pattern 2: Selection of Edge Server (UC/MC) 91

FIG. 5 illustrates an example of a control sequence for a multicaststream.

The edge server (MC/UC) 92 requests stream information such as thetransmission rate, the source (S) address, the group (G) address, theport, the priority, and the like of content from the edge server (UC/MC)91 using “(1) multicast stream information request” with the speedinformation of the stream that the edge server (MC/UC) can receive Here,the request destination of “(1) multicast stream information request”may be a different apparatus from the edge server (UC/MC) 91 thatmanages the multicast stream information. Further, “(1) multicast streaminformation request” may be made using a content request from the UE 94connected to the edge server (MC/UC) 91.

The edge server (UC/MC) 91 selects an optimal single stream from aplurality of pieces of stream information to be distributed based on theinformation of the rate of the stream that can be received by the edgeserver (MC/UC) 92 using “(2) multicast stream information response” andresponds with only the information of the selected stream. Here, theresponse source of “(2) multicast stream information response” may be adifferent apparatus from the edge server (UC/MC) 91 that manages themulticast stream information.

The edge server (MC/UC) 92 requests distribution of the multicast streamaccording to “(2) multicast stream information response” from the router95 or the like on the network that performs transfer in multicast inmulticast Join, or the like using “(3) Join processing”. This allowsdistribution of the multicast stream selected from the router 95 or thelike. For “(3) Join processing”, for example, a protocol such as IGMP orMLD can be used.

The edge server (MC/UC) 92 requests distribution of the multicast streamaccording to “(2) multicast stream information response” from the edgeserver (UC/MC) 91 using “(4) multicast stream request”. Here, therequest destination of “(4) multicast stream request” may be a differentapparatus from the edge server (UC/MC) that manages the multicast streaminformation. In this case, the apparatus that manages multicast streaminformation can request distribution of the multicast stream requestedfrom the edge server (MC/UC) 92 with respect to the edge server (UC/MC)91 in continuation of “(4) multicast stream request”.

Here, the order of “(3) Join processing” and “(4) multicast streamrequest” may be reversed. In addition, “(3) Join processing” may beomitted in the case of a network on which a static multicast route hasbeen built. Furthermore, “(1) multicast stream information request” and“(2) multicast stream information response” can be omitted if themulticast stream information is known or predetermined.

In addition, “(2) multicast stream information response” may include thefact that distribution is completed if the corresponding multicaststream has already been distributed due to a request from another edgeserver (MC/UC) 92. Furthermore, “(4) multicast stream request” may beomitted.

The edge server (UC/MC) 91 distributes the requested stream in “(5)multicast stream”, and the edge server (MC/UC) 92 receives the stream.Further, when the corresponding multicast stream has already beendistributed due to a request from another edge server (MC/UC) 92, thenew distribution can be omitted.

The edge server (MC/UC) 92 can notify the edge server (UC/MC) 91 ofstopping or completion of the reception of the multicast stream using“(6) notification of stop/completion of reception of multicast stream”.Here, the notification destination of “(6) notification ofstop/completion of reception of multicast stream” may be a differentapparatus from the edge server (UC/MC) 91 that manages the multicaststream information. In this case, the apparatus that manages themulticast stream information can notify the edge server (MC/UC) 92 ofthe multicast stream information notified from the edge server (UC/MC)91 in continuation of “(6) notification of stop/completion of receptionof multicast stream”. Further, with respect to (6), in a case in which“(4) multicast stream request” times out, a long time is being taken for“(5) multicast stream”, or the like, continuation of viewing such as akeepalive may be notified from the edge server (MC/UC) 92 in the middleof receiving “(5) multicast stream” and this may replace or be used incombination according to the time-out. Further, in a case in whichdistribution of the same multicast stream to other edge servers (MC/UC)92 continues, the distribution is not stopped, and only in a case inwhich reception by all edge servers (MC/UC) 92 is stopped/finished, canthe distribution of the multicast be stopped.

The edge server (MC/UC) 92 notifies the router 95 on the network thatperforms transfer in multicast of the fact that the reception of theselected multicast stream has finished in multicast Join, or the like,using “(7) Leave processing”. This allows the distribution of themulticast stream selected from the router 95 or the like to be stopped.For “(7) Leave processing”, for example, a protocol such as IGMP or MLDcan be used.

Here, the order of “(6) notification of stop/completion of reception ofmulticast stream” and “(7) Leave processing” may be reversed. Inaddition, “(7) Leave processing” may be omitted in the case of a networkon which a static multicast route has been built.

A single stream may be composed of multiple sub-streams. In a case ofaddresses, for example, a single combination (S1, G1) may be considereda single stream 1, and a combination of multiple addresses {(S1, G1),(S2, G2)} may be considered a single stream.

Multiple files may be processed as the same multicast stream. Forexample, there is a case in which one piece of content is stored asdivided multiple files in the origin, or the like. In this case, theycan be regarded as the same multicast stream in terms of the common URL,or the like.

Sequence Pattern 3

The sequence pattern 1 and the sequence pattern 2 may be used incombination. In this case, in selection according to the sequencepattern 2, a plurality of streams may be selected and notified, ratherthan selecting a single stream.

Multicast Stream Information Response

Selection Response 1 of Multicast Stream Information Response

The above-described multicast stream information included in “(2)multicast stream information response” of the edge server (UC/MC) 91 maybe selectively included in the response based on other information suchas a load on the edge server (UC/MC) 91, a network load imposed from anetwork operation system, or the like, packet reception errorinformation obtained from the edge server (MC/UC) 92 with respect topreviously transmitted packets, and the like, regardless of the contentof “(1) multicast stream information request”. For example, in a case inwhich high-rate stream 1 is determined to be unsuitable for transmissionbased on the information when three streams of high-rate stream 1,mid-rate stream 2, and low-rate Stream 3 are provided, only mid-ratestream 2 and low-rate stream 3 can be transmitted. Such a selectiveresponse is used when it is considered that transmission of a high-ratestream is likely to cause a load, such as congestion, on the network orwhen it is difficult for the edge server (MC/UC) 92 to receive thestream. Therefore, transmission and/or reception with these adverseeffects eliminated can be performed.

Selection Response 2 of Multicast Stream Information Response

The above-described multicast stream information included in “(2)multicast stream information response” of the edge server (UC/MC) 91 maybe dynamically changed and then included in the response based on otherinformation such as a load on the edge server (UC/MC) 91, a network loadimposed from a network operation system, or the like, packet receptionerror information obtained from the edge server (MC/UC) 92 with respectto previously transmitted packets, and the like, regardless of thecontent of “(1) multicast stream information request”. For example, in acase in which the transmission rate of the current stream is determinedto be unsuitable based on the information when three streams ofhigh-rate stream 1, mid-rate stream 2, and low-rate stream 3 areprovided, rates may be newly set again to change them as high-ratestream 1′, mid-rate Stream 2′, and low-rate Stream 3′. Theabove-described case includes a change to a lower rate and a change to ahigher rate. In addition, a new stream with another rate may also beadded.

Such a dynamically changed response to the information of the streamchanged to have a lower transmission rate is used when it is consideredthat transmission of a high-rate stream is likely to cause a load, suchas congestion, on the network, or when it is difficult for the edgeserver (MC/UC) 92 to receive the stream. Therefore, transfer with theseadverse effects eliminated can be performed.

Such a dynamically changed response to the information of the streamchanged to have a higher transmission rate or additional information ofa stream with a new rate is used when it is considered that ahigher-rate stream can be transmitted on the network or when it isconsidered that the edge server (MC/UC) 92 can receive the stream.Therefore, transfer with a lower latency can be performed.

Expansion Method

The multicast stream may be a multi-layer multicast stream. One streamof the multi-layer multicast stream will be referred to as a layer here.

Specifically, the edge server (UC/MC) 91 on the transmission sidedivides the input content and transmits each of the divided streams atthe highest transfer rate of different transfer rates. The edge servers(MC/UC) 92A, 92B, and 92C on the reception side receive each of thestreams at a desired transfer rate. The edge servers (MC/UC) 92A, 92B,and 92C have different reception rates, which results in a stream thatcannot be received by any of the edge servers (MC/UC) 92A, 92B, and 92C.For example, the edge servers (MC/UC) 92B and 92C among the edge servers(MC/UC) 92A, 92B, and 92C may not be able to receive a stream. For thisreason, the edge server (UC/MC) 91 on the transmission side sequentiallyre-transmits some streams, which cannot be received by the edge servers(MC/UC) 92B and 92C at their highest transfer rate, at a transfer rateat which the edge servers (MC/UC) 92B and 92C on the reception side canreceive.

FIG. 6 illustrates an overview of an example of a group of two receptionrates. The edge server (UC/MC) 91 generates layer 1, layer 2, and layer3 for file 1. At this time, the file 1 can be restored by completing thereception of the layer 1 and the layer 2, or the reception of the layer1 and the layer 3. Here, the layer 1 and the layer 2 are set as a layergroup A, and the layer 1 and the layer 3 are set as a layer group B.

Further, packets of the layer 1 and the layer 2 are transmitted in analternating manner, and the layer 3 is transmitted after thetransmission of the layer 1 is completed. For example, if the layer 1,the layer 2, and the layer 3 have equal data size and packet size, andhave the same transmission rate, the layer group A of the file 1 canhave a double transfer rate and a half of the transfer latency, comparedto the layer group B. Further, the alternating manner mentioned here isnot necessarily an alternating manner for every packet, and can be analternating manner for N packets of the layer 1 and M packets of thelayer 2.

The edge server (MC/UC) 92A is equipment with a high-rate orhigh-performance network for reception in the multicast communicationthat selectively receives the layer group A, and the edge server (MC/UC)92B is equipment with a low-rate or low-performance network forreception in the multicast communication that selectively receives thelayer group B. In other words, this is a mechanism in which some data isshared as layers by reception groups with different reception rates.This allows content to be distributed with a lower latency in accordancewith the reception capacity of the network or the edge servers (MC/UC)92. In addition, the amount of data to be transmitted can be reduced inaccordance with the reception capacity of the network or the edgeservers (MC/UC) 92, compared to a case in which streams are transmittedseparately.

Each layer such as the layer 1, the layer 2, and the layer 3 areselectively received and transferred by equipment at which the layer isrouted such as the edge servers (MC/UC) 92 or the router 95 on thenetwork because the layers have a difference in part of the headers ofpackets other than data such as the source address, the group address,the port, or the priority as well as the transmission rate.

Selective multicast reception of the layers with different sourceaddresses or group addresses may be controlled by the edge servers(MC/UC) 92 using a dynamic multicast route control technique such asIGMP, MLD, or the like. Thus, only a stream selected by the edge server(MC/UC) 92 is selectively transferred by network equipment, such as therouter 95, and thus a layer not selected by the edge server (MC/UC) 92is not distributed to the corresponding edge server (MC/UC) 92. Even forthe control of a static multicast route, control of the pseudo-dynamicmulticast route can also be performed in conjunction with an operationsystem of the network equipment. In addition, in a case of a staticmulticast route, a route for a high-rate group and a route for alow-rate group may be set in advance. Furthermore, the number of groupsmay be three or more.

As a result, the amount of traffic resulting from transmission of theorigin server 93 and the edge server (UC/MC) 91 can be reduced to thenumber of multicast streams for content for approximately the number ofpieces of UE, compared to unicast distribution. While the amount oftraffic increases to approximately a multiple of the number of multicaststreams for the content, compared to that in the multicast conversiontechniques of the related art (NPL 3 and NPL 4), a sufficient amount oftraffic with respect to the server and the network can sufficiently bereduced, considering the fact that the number of pieces of UE is verylarge.

Moreover, the amount of traffic can be reduced and more stabled and highimage quality videos can be distributed by sharing the layers, comparedto a method in which layers are not shared.

When there is no UE 94 to connect, the edge server (MC/UC) 92C does notreceive stream distribution and thus receives no stream, however, whenthere is the UE 94 to connect, the edge server can receive any stream byperforming similar processing to that of any of the edge server 92A or92B. Further, the number of edge servers (MC/UC) 92 is not limited tothree, and may be multiple.

This method is not based on the premise of hierarchy/scalability bycodecs and is not dependent on details of content (files), but canrealize scalability of a transfer rate.

Layer

In the present embodiment, content (a file/a stream) is divided into mlayers and received in o groups. The example of FIG. 7 illustrates acase in which content is divided into three layers and received in twogroups. Here, (1)-i indicates i-th data of layer 1, (2)-j indicates j-thdata of layer 2, and (3)-k indicates k-th data of layer 3.

The content (file/stream) is divided into data having a size that can betransferred as packets from (1)-1, (2)-1, and (3)-1 to (1)-n, (2)-n, and(3)-n. Here, the data of the layer 2 and the data of the layer 3 are thesame data. Further, when the content size is not a multiple of 2n, thenumber of packets allocated to each layer may be different. Each layerhas different headers such as a source address, group address, port, andpriority to distinguish reception.

In the data transmission, the data of the layer 1 and the data of thelayer 2 are alternately transmitted at intervals of t1 in phase 1, andin phase 2 after the transmission of the layers 1 and 2 is completed,the data of the layer 3 is transmitted at intervals of t2 that is equalto 2×t1.

Terminals of a group A receive packets of (1)-1 and (2)-1 to (1)-n and(2)-n of the layers 1 and 2 at the intervals of t1, in other words, theterminals complete reception of the content for the time of 2n×t1 in thephase 1.

Terminals of a group B receive packets of (1)-1 and (3)-1 to (1)-n and(3)-n of the layers 1 and 3 at the intervals of t2, in other words, theterminals complete reception of the content for the time of 2n×t2(=4n×t1) in the phase 2.

In this case, a reception rate Sa of the group A and the reception rateSb of the group B satisfy the relationship ofSa/Sb=(2n×t2)/(2n×t1)=t2/t1=(2×t1)/t1=2. Thus, although the data istransmitted to the two groups at different rates, the amount oftransmitted data increases just by 1.5 times compared to the case inwhich data is transmitted to a single group.

Further, the order of transmission of the packets in each phase can bechanged. In addition, the location and order of allocation of the layerscan be changed within the content.

Layer Pattern

An example of a layer pattern in a case in which the number of receptiongroups is two is illustrated in FIG. 8 .

An example of a layer pattern in a case in which the number of receptiongroups is three is illustrated in FIG. 9 .

Apparatus Configuration

An exemplary configuration of the edge server (UC/MC) 91 and the edgeserver (MC/UC) 92 for forming the above-described systems is illustratedin FIG. 10 . However, other configurations may be used to form thesystem described above.

The edge server (UC/MC) 91 includes a unicast file acquisition unit 15,a storage 12, a multicast transmission unit 14, a control unit 11, and acontrol communication unit 14. The edge server (UC/MC) 91 can berealized by a computer and a program, and the program can be recorded ona recording medium or provided through a network.

The unicast file acquisition unit 15 can acquire files from the origin93 in unicast communications and store it in the storage 12. Inaddition, the unicast file acquisition unit 15 can request a file fromthe origin 93 in accordance with an instruction from the control unit11. The storage 12 is a computer resource that can store data, such as aHDD, an SSD, a memory, or the like.

The multicast transmission unit 14 can read files from the storage 12and transmit the files as multicast packet according to an instructionfrom the control unit 11. In addition, the multicast transmission unit14 can transmit data of one file as a plurality of streams or layerswith different transmission rates according to an instruction from thecontrol unit 11. Furthermore, FEC information can be added to thetransmission data.

The control communication unit 14 can receive (1) multicast streaminformation request from the edge server (MC/UC) 92 and transfer theinformation to the control unit 11. In addition, the controlcommunication unit 14 can transmit (2) multicast stream informationresponse to the edge server (MC/UC) 92 according to an instruction fromthe control unit 11. Furthermore, the control communication unit 14 canreceive (4) multicast stream request from the edge server (MC/UC) 92 andtransfer the information to the control unit 11. In addition, thecontrol communication unit 14 can receive (6) notification ofstop/completion of reception of multicast stream from the edge server(MC/UC) 92 and transfer the information to the control unit 11. Thecontrol unit 11 can perform the above-described control over themulticast transmission unit 13 and the control communication unit 14. Inaddition, in a case in which the requested file does not stored in thestorage, the control unit 11 can instruct the unicast file acquisitionunit 15 to request the file from the origin.

The edge server (MC/UC) 92 includes a unicast file transmission unit 26,a storage 222, a multicast reception unit 23, a control unit 21, and acontrol communication unit 24. The edge server (MC/UC) 92 can berealized by a computer and a program, and the program can be recorded ona recording medium or provided through a network.

Receiving a request for a file from the UE 94, the unicast filetransmission unit 92 can transmit the file in the storage 22 to the UE94 in unicast communication. Furthermore, when the file is not stored inthe storage 22, the unicast file transmission unit 92 can notify thecontrol unit 21 that the file is not stored in the storage 22. Inaddition, the unicast file transmission unit 92 can monitor the storage22 or know generation of a file to be transmitted to the UE 94 from thenotification from the control unit 21, and then read the file from thestorage 22 to transmit the file to the UE 94 in unicast communication.

The storage 22 is a computer resource that can store data, such as aHDD, an SSD, a memory, or the like.

The multicast reception unit 23 can receive files from the multicasttransmission unit 13 and write the files into the storage 22. Inaddition, information related to reception states, such as packet lossinformation can be notified to the control unit. Further, theinformation can be notified to the control unit 21 based on a requestfrom the control unit 11. In addition, received data may be subject toerror correction and detection using FEC information.

The control communication unit 24 can transmit (1) multicast streaminformation request to the edge server (UC/MC) 91 according to aninstruction from the control unit 21. In addition, the edge server canreceive (2) multicast stream information response from the edge server(UC/MC) 91 and transfer the information to the control unit 24.Furthermore, a packet for (3) Join processing can be transmitted to anearby router 95 with packet reachability, or the like based on aninstruction from the control unit 21. In addition, (6) notification ofstop/completion of reception of multicast stream can be transmitted tothe edge server (UC/MC) 91 based on an instruction from the control unit24. Furthermore, a packet for (7) Leave processing can be transmitted tothe nearby router 95 with packet reachability, or the like based on aninstruction from the control unit 24.

The control unit 21 can perform the above-described control over themulticast reception unit 23 and the control communication unit 24.Furthermore, the control unit 21 can instruct the control communicationunit 24 for (1) multicast stream information request based on a requestfrom the unicast file transmission unit 25.

Effects Obtained from the Present Disclosure

Content can be distributed with a low latency in the multicastcommunication to the edge servers (MC/UC) 92 connected to a network withhigh rate and stability and the edge servers (MC/UC) 92 with a highmulticast reception capacity, without being restricted by other low-rateand unstable networks, or the edge servers (MC/UC) 92 with a lowcapacity. In addition, stable content can be distributed to low-rate andunstable networks and edge servers (MC/UC) 92 with a low capacity.

Furthermore, as a result, a network for homogeneous multicasttransmission may not be needed, management of QoS may not be needed, oran unstable wireless multicast network may be used. Similarly, an edgeserver (MC/UC) 92 with a low capacity that does not need management maybe used.

In particular, content with the same image quality can be distributedwhile controlling the quality of latency in accordance with a state of anetwork or a terminal.

In the expansion method, by sharing part of data with reception groupshaving different rates as layers, the above-described effects can beexhibited with a smaller amount of data transmission than the number ofreception groups. In addition, this method is not based on the premiseof hierarchy/scalability by codecs and is not dependent on details ofthe content (files), but can achieve scalability of a transfer rate.

Points of the Present Disclosure

When the number of viewers is large, live HTTP streaming tends togenerate a load with a peak on a distribution server or network, andthus QoE in viewing the video is easily deteriorated. On the contrary,while a multicast conversion technique for some relevant sections bringsthe effect of reducing the amount of traffic, if there is some equipmentthat needs to delay reception in the multicast communication, theoverall transfer latency increases. As a result, in order to reduce sucha transfer latency, equipment with a high rate, stability, and highperformance in multicast reception has been required on an availablenetwork.

The present disclosure enables a plurality of multicast streams of onepiece of content having different transfer rates to be generated usingthe multicast conversion technique for some relevant sections and thusenables various networks and low-performance multicast receptionequipment that have low rate and are not manageable or for wirelesscommunication to be used while maintaining sufficient traffic reductioneffects.

In particular, the method in which content with the same image qualitycan be controlled for the quality of latency and distributed inaccordance with a state of a network or a terminal has never beenbefore.

INDUSTRIAL APPLICABILITY

The present disclosure can be applied in the information andtelecommunication industry.

REFERENCE SIGNS LIST

-   91 Edge server (UC/MC)-   11 Control unit-   12 Storage-   13 Mar control communication unit-   14 Ticast transmission unit-   15 Unicast file acquisition unit-   21 Control unit-   22 Storage-   23 Multicast reception unit-   24 Control communication unit-   25 Unicast file transmission unit-   92 Edge server (MC/UC)-   93 Origin-   94 UE-   95 Router

1. A content distribution system for converting part of communicationfor distribution into multicast communication, the content distributionsystem comprising: a transmission-side edge server configured to convertunicast communication into multicast communication and performtransmission to a multicast communication network; and a reception-sideedge server configured to convert the multicast communicationtransmitted on the multicast communication network into unicastcommunication, wherein the transmission-side edge server generates andtransmits a plurality of multicast streams having a plurality ofdifferent transfer rates for a same input content, and thereception-side edge server selects and receives a multicast streamhaving a desired transfer rate among the plurality of transmittedmulticast streams.
 2. The content distribution system according to claim1, wherein the transmission-side edge server divides the input content,transmits, at a highest transfer rate among the plurality of differenttransfer rates, a plurality of streams obtained by the division, andsequentially re-transmits part of the plurality of streams which are notreceived by the reception-side edge server at the highest transfer rate,at a transfer rate at which the reception-side edge server can receive,and the reception-side edge server receives each of the plurality ofstreams at a desired transfer rate.
 3. A content distribution methodperformed by a content distribution system for converting part ofcommunication for distribution into multicast communication, the contentdistribution system comprising a transmission-side edge serverconfigured to convert unicast communication into multicast communicationand perform transmission to a multicast communication network, and areception-side edge server configured to convert the multicastcommunication transmitted on the multicast communication network intounicast communication, the method comprising: by the transmission-sideedge server, generating and transmitting a plurality of multicaststreams having a plurality of different transfer rates for a same inputcontent, and by the reception-side edge server, selecting and receivinga multicast stream having a desired transfer rate among the plurality oftransmitted multicast streams.
 4. An edge server apparatus included in acontent distribution system for converting part of communication fordistribution into multicast communication, wherein the edge serverapparatus is a transmission-side edge server configured to convertunicast communication into multicast communication and performtransmission to a multicast communication network, and the edge serverapparatus generates a plurality of multicast streams having differenttransfer rates for a same content received in the unicast communication,and transmits the plurality of generated multicast streams to themulticast communication network.
 5. (canceled)
 6. A non-transitorycomputer-readable medium having computer-executable instructions that,upon execution of the instructions by a processor of a computer, causethe computer to function as the edge server apparatus according to claim4.